﻿// Copyright (c) 2016, Dijji, and released under Ms-PL.  This can be found in the root of this distribution. 
// Tables and implementation approach from libpff under LGPLv3+: https://github.com/libyal/libpff  Copyright (c) 2008-2012, Joachim Metz <joachim.metz@gmail.com>

using System;

namespace XstReader
{
    // Support for decrypting data areas of xst files, based on the algorithm description in <MS-PST>
    // Tables taken from libpff, as a more convenient form

    class Crypto
    {
        static byte[] Compressible = new byte[] {
	        0x47, 0xf1, 0xb4, 0xe6, 0x0b, 0x6a, 0x72, 0x48, 0x85, 0x4e, 0x9e, 0xeb, 0xe2, 0xf8, 0x94, 0x53,
	        0xe0, 0xbb, 0xa0, 0x02, 0xe8, 0x5a, 0x09, 0xab, 0xdb, 0xe3, 0xba, 0xc6, 0x7c, 0xc3, 0x10, 0xdd,
	        0x39, 0x05, 0x96, 0x30, 0xf5, 0x37, 0x60, 0x82, 0x8c, 0xc9, 0x13, 0x4a, 0x6b, 0x1d, 0xf3, 0xfb,
	        0x8f, 0x26, 0x97, 0xca, 0x91, 0x17, 0x01, 0xc4, 0x32, 0x2d, 0x6e, 0x31, 0x95, 0xff, 0xd9, 0x23,
	        0xd1, 0x00, 0x5e, 0x79, 0xdc, 0x44, 0x3b, 0x1a, 0x28, 0xc5, 0x61, 0x57, 0x20, 0x90, 0x3d, 0x83,
	        0xb9, 0x43, 0xbe, 0x67, 0xd2, 0x46, 0x42, 0x76, 0xc0, 0x6d, 0x5b, 0x7e, 0xb2, 0x0f, 0x16, 0x29,
	        0x3c, 0xa9, 0x03, 0x54, 0x0d, 0xda, 0x5d, 0xdf, 0xf6, 0xb7, 0xc7, 0x62, 0xcd, 0x8d, 0x06, 0xd3,
	        0x69, 0x5c, 0x86, 0xd6, 0x14, 0xf7, 0xa5, 0x66, 0x75, 0xac, 0xb1, 0xe9, 0x45, 0x21, 0x70, 0x0c,
	        0x87, 0x9f, 0x74, 0xa4, 0x22, 0x4c, 0x6f, 0xbf, 0x1f, 0x56, 0xaa, 0x2e, 0xb3, 0x78, 0x33, 0x50,
	        0xb0, 0xa3, 0x92, 0xbc, 0xcf, 0x19, 0x1c, 0xa7, 0x63, 0xcb, 0x1e, 0x4d, 0x3e, 0x4b, 0x1b, 0x9b,
	        0x4f, 0xe7, 0xf0, 0xee, 0xad, 0x3a, 0xb5, 0x59, 0x04, 0xea, 0x40, 0x55, 0x25, 0x51, 0xe5, 0x7a,
	        0x89, 0x38, 0x68, 0x52, 0x7b, 0xfc, 0x27, 0xae, 0xd7, 0xbd, 0xfa, 0x07, 0xf4, 0xcc, 0x8e, 0x5f,
	        0xef, 0x35, 0x9c, 0x84, 0x2b, 0x15, 0xd5, 0x77, 0x34, 0x49, 0xb6, 0x12, 0x0a, 0x7f, 0x71, 0x88,
	        0xfd, 0x9d, 0x18, 0x41, 0x7d, 0x93, 0xd8, 0x58, 0x2c, 0xce, 0xfe, 0x24, 0xaf, 0xde, 0xb8, 0x36,
	        0xc8, 0xa1, 0x80, 0xa6, 0x99, 0x98, 0xa8, 0x2f, 0x0e, 0x81, 0x65, 0x73, 0xe4, 0xc2, 0xa2, 0x8a,
	        0xd4, 0xe1, 0x11, 0xd0, 0x08, 0x8b, 0x2a, 0xf2, 0xed, 0x9a, 0x64, 0x3f, 0xc1, 0x6c, 0xf9, 0xec
        };

        static byte[] Cyclic1 = new byte[] {
            0x41, 0x36, 0x13, 0x62, 0xa8, 0x21, 0x6e, 0xbb, 0xf4, 0x16, 0xcc, 0x04, 0x7f, 0x64, 0xe8, 0x5d,
            0x1e, 0xf2, 0xcb, 0x2a, 0x74, 0xc5, 0x5e, 0x35, 0xd2, 0x95, 0x47, 0x9e, 0x96, 0x2d, 0x9a, 0x88,
            0x4c, 0x7d, 0x84, 0x3f, 0xdb, 0xac, 0x31, 0xb6, 0x48, 0x5f, 0xf6, 0xc4, 0xd8, 0x39, 0x8b, 0xe7,
            0x23, 0x3b, 0x38, 0x8e, 0xc8, 0xc1, 0xdf, 0x25, 0xb1, 0x20, 0xa5, 0x46, 0x60, 0x4e, 0x9c, 0xfb,
            0xaa, 0xd3, 0x56, 0x51, 0x45, 0x7c, 0x55, 0x00, 0x07, 0xc9, 0x2b, 0x9d, 0x85, 0x9b, 0x09, 0xa0,
            0x8f, 0xad, 0xb3, 0x0f, 0x63, 0xab, 0x89, 0x4b, 0xd7, 0xa7, 0x15, 0x5a, 0x71, 0x66, 0x42, 0xbf,
            0x26, 0x4a, 0x6b, 0x98, 0xfa, 0xea, 0x77, 0x53, 0xb2, 0x70, 0x05, 0x2c, 0xfd, 0x59, 0x3a, 0x86,
            0x7e, 0xce, 0x06, 0xeb, 0x82, 0x78, 0x57, 0xc7, 0x8d, 0x43, 0xaf, 0xb4, 0x1c, 0xd4, 0x5b, 0xcd,
            0xe2, 0xe9, 0x27, 0x4f, 0xc3, 0x08, 0x72, 0x80, 0xcf, 0xb0, 0xef, 0xf5, 0x28, 0x6d, 0xbe, 0x30,
            0x4d, 0x34, 0x92, 0xd5, 0x0e, 0x3c, 0x22, 0x32, 0xe5, 0xe4, 0xf9, 0x9f, 0xc2, 0xd1, 0x0a, 0x81,
            0x12, 0xe1, 0xee, 0x91, 0x83, 0x76, 0xe3, 0x97, 0xe6, 0x61, 0x8a, 0x17, 0x79, 0xa4, 0xb7, 0xdc,
            0x90, 0x7a, 0x5c, 0x8c, 0x02, 0xa6, 0xca, 0x69, 0xde, 0x50, 0x1a, 0x11, 0x93, 0xb9, 0x52, 0x87,
            0x58, 0xfc, 0xed, 0x1d, 0x37, 0x49, 0x1b, 0x6a, 0xe0, 0x29, 0x33, 0x99, 0xbd, 0x6c, 0xd9, 0x94,
            0xf3, 0x40, 0x54, 0x6f, 0xf0, 0xc6, 0x73, 0xb8, 0xd6, 0x3e, 0x65, 0x18, 0x44, 0x1f, 0xdd, 0x67,
            0x10, 0xf1, 0x0c, 0x19, 0xec, 0xae, 0x03, 0xa1, 0x14, 0x7b, 0xa9, 0x0b, 0xff, 0xf8, 0xa3, 0xc0,
            0xa2, 0x01, 0xf7, 0x2e, 0xbc, 0x24, 0x68, 0x75, 0x0d, 0xfe, 0xba, 0x2f, 0xb5, 0xd0, 0xda, 0x3d
        };

        static byte[] Cyclic2 = new byte[] {
            0x14, 0x53, 0x0f, 0x56, 0xb3, 0xc8, 0x7a, 0x9c, 0xeb, 0x65, 0x48, 0x17, 0x16, 0x15, 0x9f, 0x02,
            0xcc, 0x54, 0x7c, 0x83, 0x00, 0x0d, 0x0c, 0x0b, 0xa2, 0x62, 0xa8, 0x76, 0xdb, 0xd9, 0xed, 0xc7,
            0xc5, 0xa4, 0xdc, 0xac, 0x85, 0x74, 0xd6, 0xd0, 0xa7, 0x9b, 0xae, 0x9a, 0x96, 0x71, 0x66, 0xc3,
            0x63, 0x99, 0xb8, 0xdd, 0x73, 0x92, 0x8e, 0x84, 0x7d, 0xa5, 0x5e, 0xd1, 0x5d, 0x93, 0xb1, 0x57,
            0x51, 0x50, 0x80, 0x89, 0x52, 0x94, 0x4f, 0x4e, 0x0a, 0x6b, 0xbc, 0x8d, 0x7f, 0x6e, 0x47, 0x46,
            0x41, 0x40, 0x44, 0x01, 0x11, 0xcb, 0x03, 0x3f, 0xf7, 0xf4, 0xe1, 0xa9, 0x8f, 0x3c, 0x3a, 0xf9,
            0xfb, 0xf0, 0x19, 0x30, 0x82, 0x09, 0x2e, 0xc9, 0x9d, 0xa0, 0x86, 0x49, 0xee, 0x6f, 0x4d, 0x6d,
            0xc4, 0x2d, 0x81, 0x34, 0x25, 0x87, 0x1b, 0x88, 0xaa, 0xfc, 0x06, 0xa1, 0x12, 0x38, 0xfd, 0x4c,
            0x42, 0x72, 0x64, 0x13, 0x37, 0x24, 0x6a, 0x75, 0x77, 0x43, 0xff, 0xe6, 0xb4, 0x4b, 0x36, 0x5c,
            0xe4, 0xd8, 0x35, 0x3d, 0x45, 0xb9, 0x2c, 0xec, 0xb7, 0x31, 0x2b, 0x29, 0x07, 0x68, 0xa3, 0x0e,
            0x69, 0x7b, 0x18, 0x9e, 0x21, 0x39, 0xbe, 0x28, 0x1a, 0x5b, 0x78, 0xf5, 0x23, 0xca, 0x2a, 0xb0,
            0xaf, 0x3e, 0xfe, 0x04, 0x8c, 0xe7, 0xe5, 0x98, 0x32, 0x95, 0xd3, 0xf6, 0x4a, 0xe8, 0xa6, 0xea,
            0xe9, 0xf3, 0xd5, 0x2f, 0x70, 0x20, 0xf2, 0x1f, 0x05, 0x67, 0xad, 0x55, 0x10, 0xce, 0xcd, 0xe3,
            0x27, 0x3b, 0xda, 0xba, 0xd7, 0xc2, 0x26, 0xd4, 0x91, 0x1d, 0xd2, 0x1c, 0x22, 0x33, 0xf8, 0xfa,
            0xf1, 0x5a, 0xef, 0xcf, 0x90, 0xb6, 0x8b, 0xb5, 0xbd, 0xc0, 0xbf, 0x08, 0x97, 0x1e, 0x6c, 0xe2,
            0x61, 0xe0, 0xc6, 0xc1, 0x59, 0xab, 0xbb, 0x58, 0xde, 0x5f, 0xdf, 0x60, 0x79, 0x7e, 0xb2, 0x8a
        };


        public static void Decrypt(ref byte[] buffer, EbCryptMethod method, UInt32 key, int offset, int length)
        {
            switch (method)
            {
                case EbCryptMethod.NDB_CRYPT_NONE:
                    return;

                case EbCryptMethod.NDB_CRYPT_PERMUTE:
                    for (int i = offset; i < offset + length; i++)
                        buffer[i] = Compressible[buffer[i]];
                    break;

                case EbCryptMethod.NDB_CRYPT_CYCLIC:
                    {
                        // We've never seen an actual example of this
                        // This is what we hope is a valid implementation 
                        UInt16 salt = (UInt16)(((key & 0xffff0000) >> 16) ^ (key & 0x0000ffff));

                        for (int i = offset; i < offset + length; i++)
                        {
                            byte lower_salt = (byte)(salt & 0x00ff);
                            byte upper_salt = (byte)((salt & 0xff00) >> 8);
                            byte index = buffer[i];
                            index += lower_salt;
                            index = Cyclic1[index];
                            index += upper_salt;
                            index = Cyclic2[index];
                            index -= upper_salt;
                            index = Compressible[index];
                            index -= lower_salt;
                            buffer[i] = index;

                            salt++;
                        }

                        // Throw until the code has been validated
                        throw new Exception("Decryption of Cyclic algorithm not validated");
                        //break;
                    }

                default:
                    throw new Exception("Encryption method not known");
            }
        }
    }
}
